Implications on the paleoecology of autochthonous lycopods in clastic sedimentary environments of the Early Pennsylvanian of Alabama

Abstract

Numerous, correlative localities throughout the Upper Cliff Coal Interval (Lower Pennsylvanian), Blount County, Alabama, have been observed in which lycopod forests are preserved. These assemblages are present in lower delta plain facies interpreted to represent (1) the abandonment phase of a distributary channel system with resultant bayou development, (2) non-peat accumulating swamps capping interdistributary bay deposition, (3) possible terminal phase of peat accumulating swamps and (4) crevasse splay deposits. Field observations in combination with sedimentological, preservational and biological evidence support the conclusion that these autochthonous Carboniferous lycopods represent a taphonomically biased assemblage of aquatic or semi-aquatic (swamp) communities. Interpretations derived from the present study in conjunction with published accounts of erect lycopods suggest that these plants could tolerate all waters from fresh to saline conditions. Periodic drying of swampy habitats may have subjected lycopods to subaerial and aerial conditions, but bulk-replaced erect lycopods predominantly inhabited water stressed conditions. The monotypic character of the lycopod forests supports the hypothesis that in the tropical lowlands of the tropical lowlands of the Carboniferous lycopods held a relatively unique, physiologically stressed position in the delta flood basin. These arborescent lycopods became established in any depositional site subject to flooding and standing water when conditions prevailed which allowed for the establishment and development of individuals.